This study is designed to evaluate the long-term safety and efficacy of Upadacitinib in participants with ulcerative colitis (UC) who have not responded at the end of the induction period in Study M14-234 Substudy 1, who have had loss of response during the maintenance period of Study M14-234 Substudy 3, or who have successfully completed Study M14-234 Substudy 3.